In the manufacture of certain printed circuit boards, a plurality of rows of closely spaced apertures in a substrate and regions of the substrate surrounding the apertures are plated by an appropriate masking-and-plating operation to form rows of small, closely spaced contact pads on either side of the board. Occasionally, however, the adjacent contact pads are too closely spaced or are actually formed together, which causes arcing or shorting between adjacent pads during use of the circuit board.
In the past, to cure this defect on the printed circuit boards, an operator would trim away the metal between the adjacent contact pads with a hand-held saw or other hand tool in an attempt to electrically isolate the pads from each other. However, this procedure was undesirable and did not produce consistent results because of the difficulty the operator experienced in accurately aligning the cutting tool between the small contact pads. Additionally, when trimming a multilayer board, the operator had to be extremely careful not to cut too deeply into the board to avoid damaging the circuit layers beneath the surface of the board. In this connection, improper aligning of the cutting tool with the contact pads and/or cutting too deeply into the board could result in the necessity for additional repair of the board or in scrapping of the board. The necessity for accurately aligning the cutting tool with the contact pads and for controlling the depth of cut also resulted in a tedious and time consuming operation.
In one material removing technique, U.S. Pat. No. 2,392,819 discloses an apparatus for grinding gear teeth on a gear wherein the teeth are to be nonrectilinear in an axial plane. The apparatus includes a grinding wheel for cutting the teeth of the gear and which is mounted on an oscillatory frame. The gear to be ground is mounted on a reciprocating table which also includes a cam member mounted thereon. A rod depends from the frame and includes a cam follower at one end thereof which moves along the surface of the cam as the table reciprocates to raise and lower the frame and the grinding wheel carried thereby, thus grinding the gear along a curved pattern which corresponds to the shape of t he cam.